Any atom based netbook you buy today is 32bit only. While new mobile atoms out early next year are allegedly going to support x64, older models will probably linger in retail/distribution until late in the year, so I think 2012 is still too early to drop 32 bit support. Hold off on that until win9.
i expect windows 8 gpu requirements to leave current netbooks outside the circle anyway, regardless of that cpu its running. thats why win7 will be such a long lasting os, because it will be the last to run on legacy hardware. i bet 10-15 years from now many of us will still have a win7 machine in our homes somewhere.